The present invention relates generally to an apparatus for removing and containing toxic or hazardous liquid or solid substances. More particularly, the present invention relates to a vacuum cleaner apparatus for removing spills of toxic or hazardous liquid and solid substances and for effectively retaining the macro- and micro-particles of the substance along with any vapor qenerated thereby.
The quick and efficient cleaning of spills of toxic or hazardous chemical substances is becoming increasingly important in both commercial and industrial applications. As more knowledge is gained of the potential hazards of certain substances, the impetus for providing an effective method for quickly and efficiently removing the dangerous substances has accelerated. Certain of these substances have been found particularly difficult to deal with since they contain both very small micro-particles and vapors which may be harmful to persons exposed to the substances. For example, the clean-up of spills of mercury or mercury compounds and various substances in the nuclear industry, such as depleted Uranium 238 (which may be used as weight in high performance military aircraft wings), residue from fuel rod manufacturing operations, fuel rod dust, and plutonium used in weapons manufacture, have posed particularly difficult problems for rapid and effective clean-up.
In addition, some applications using toxic or hazardous substances are on an extremely small scale. Accordingly, an apparatus which may be useful for large scale industrial applications may not be suitable for small scale clean-ups. For such small scale clean-ups, a small, relatively compact and easily movable cleaner apparatus must be provided. Such small scale applications may include, for example, the use of mercury or other toxic or hazardous substances by dentists or laboratory technicians. A further requirement for a cleaner for such small spills is that the cleaner be relatively inexpensive to purchase.
One known vacuum cleaner apparatus particularly adapted for recovering and containing mercury spills is manufactured by Nilfisk of America, Inc. of Malvern, Pa. This apparatus (which will be described in greater detail with reference to FIG. 1 of the drawings) includes a large stand-up housing with a suction motor arranged near an outlet of the housing to draw air and entrained substances in and through an inlet. A flexible hose is connected to the inlet of a centrifugal droplet separator which is connected to the housing inlet. The centrifugal droplet separator receives incoming fluid flow from the hose generally tangentially and swirls the fluid within the separator such that heavy particles, particularly of liquid mercury, drop to the bottom into a container in the separator. Thereafter, the air passes through the housing inlet and through a filter bag (usually of paper) arranged within the housing. Since the separator primarily only removes macro-particles of the liquid mercury or mercury compounds, an additional micro-filter disc is arranged downstream of the disposable bag. This filter disc is adapted to remove the micro-particles of the liquid mercury or mercury compounds and may comprise a glass fiber filter. Arranged downstream of the filter disc is an activated carbon filter which removes mercury vapor entrained in the fluid flow (i.e., the air flow) prior to exhausting the flowing fluid to the atmosphere. It should be noted that the elimination of vapors is particularly important in mercury and other substance which generate a substantial quantity of vapor at ambient pressure and even at less than ambient temperature.
The above-described mercury vacuum cleaner has certain disadvantages for smaller applications. In particular, the apparatus is particularly large and cumbersome to store and/or move close to the location of the spill. In addition, regular maintenance, such as cleaning, emptying, etc., must be performed on the various elements of the system. In particular, the centrifugal droplet separator must be periodically emptied along with the disposable bag within the housing. Also, periodic checks upon the efficiency of the glass fiber filter disc and the activated carbon filter must be undertaken. Moreover, the cost of such a large system, which is particularly useful in industrial applications, is likely to be too high for smaller spills of toxic substances such as those encountered in a laboratory or in a dental office.
Also known in the prior art are various vacuum cleaner arrangements including serially arranged filtration systems for ensuring a complete removal of unwanted particles, usually dust and other fine particles. Vacuum cleaner arrangements such as these with multiple filtration stages or elements are disclosed in U.S. Pat. Nos. 1,918,764 issued to Ljungquist; 3,046,718 issued to Ide et al; 3,308,609 issued to McCulloch et al; 3,621,640 issued to Ohno et al; 3,653,189 issued to Miyake et al; 3,665,683 issued to Schaefer; 3,835,626 issued to Miyake et al; 3,871,847 issued to Fish; and 4,229,193 issued to Miller. None of these devices is particularly adapted for removing and retaining toxic or hazardous substances particularly those substances which generate a high proportion of dangerous vapors which must be removed prior to exhausting air from the cleaner.
Accordingly, it is an object of the present invention to provide an improved apparatus for removing and retaining toxic or hazardous liquid or solid substances. More particularly, it is an object of the present invention to provide an apparatus for more effectively, efficiently and less expensively removing such substances.
Still a further object of the present invention is to provide an apparatus which is safe during operation and permits easy disposal of the toxic or hazardous substance in an acceptable manner. Yet a further object of the present invention is to provide such an apparatus in the form of a vacuum cleaner which is relatively small in size and relatively inexpensive to produce.
These objects and others are accomplished by the apparatus according to the present invention. The apparatus includes a container or housing having an inlet for the toxic or hazardous substances and an arrangement for creating suction pressure to draw the substance into the container entrained in a fluid flow created by the suction pressure. A first single filter retains both macro- and micro-particles of the substance while permitting outflow of substantially only vapors of the substance entrained in the fluid flow. The first filter is arranged downstream from and adjacent to the inlet. A second filter arranged downstream of the first unitary filter is adapted to directly receive the vapors from the first filter and to retain the vapors of the substance.
In a preferred embodiment, the first filter is secured to a downstream side of the inlet and includes a reservoir portion arranged below the inlet. The walls of the first filter permit outflow of substantially only vapors of the substance entrained within the fluid flow created by the suction arrangement. In a preferred embodiment, the first filter includes a microporous filter membrane laminated to a fibrous support structure. In a particularly preferred embodiment, the microporous membrane is comprised of polytetrafluoroethylene (PTFE) which may be readily formed into a membrane having an appropriately small pore size to retain the micro-particles of the toxic substance and is substantially chemically inert such that damage to the membrane by contact with the toxic or hazardous substance is avoided and/or minimized. Moreover, a microporous membrane of polytetrafluoroethylene does not require an unacceptably large pressure differential to draw fluid, particularly gases, through the membrane. Therefore, an increase in the power required by the suction motor is not necessary to obtain the advantages of the present invention.
Further in the preferred embodiment of the present invention, the first filter element includes an inlet portion adapted to surround an inlet duct of a vacuum cleaner having a suction motor for drawing in the substance. An enlarged portion of the filter element having walls surrounding an internal space is sealingly connected to a downstream end of the inlet portion. At least an inside surface of the walls include the microporous membrane which retains the macro- and micro-particles of the substance and permits passage of substantially only gaseous vapors of the substance through the membrane. The inlet portion and the enlarged portion are preferably comprised of the same material with the enlarged portion being sealingly connected to the inlet portion by a sewn seam over which a suitable sealant is applied to prevent passage of the air therethrough. Further, the enlarged portion is preferably in the form of a hollow cylinder coaxial with the circular inlet portion.
In accordance with still a further aspect of the present invention, a hose member adapted for connection to the inlet includes walls with a smooth continuous internal surface having a first, generally constant thickness. The hose member has a nozzle portion at a second end thereof with the nozzle portion having a second thickness substantially less than the first thickness at least at a free end of the nozzle. Preferably, the entire hose and the nozzle portion are one piece comprised of the same material, such as a plastic material which is resistant to mercury and other toxic substances. Further, the reduced thickness of the nozzle portion provides a highly flexible free end for the nozzle.